The invention relates to a method for monitoring/adjusting production in a knitting machine, and a monitoring/adjusting device therefor.
In the knitting technology, electronic data processing is increasingly employed not only for machine control purposes but also for monitoring/adjusting the production. Furthermore, it is conventional to establish a masterpiece by calculating or producing on the basis of target yarn amounts and to use the masterpiece as a reference for the production of a machine or of an entire machine series. In this case comparisons are carried out with the masterpiece, e.g. with the help of the consumed yarn amounts and/or the developments of the yarn consumption. The yarn consumption is an important aspect for a knitting mill and the specialised personnel. In case of simple, plain knitted and straight tube fabrics and equipment of the circular knitting machine with positive feeding devices, the yarn tensions vary. However, the yarn amounts remain constant in relation to the machine speed such that it does not cause any problems with respect to monitoring and evaluating the yarn consumption. Furthermore, methods exist according to which the yarn amount is measured by means of a measuring roll running in the yarn path, and according to which the measured values are evaluated centrally, however, such methods require excessively high technical efforts and complicate the re-setting, adjustment and changing of the machine setting considerably.
In a device known from EP 0 452 800 A the respective yarn amount is determined and evaluated centrally with the help of measurements of the yarn speed by means of special sensors in the yarn path. The yarn amounts consumed in the masterpiece are used for comparisons with the knitted goods in order to detect and display erroneous uses, incorrect yarn speeds and incorrect machine operation cycles.
In the case of jacquard goods or so-called body stockings, however, non-positive feeding devices of different types operating with different yarn conveying principles are used for different yarn qualities, sometimes even of different producers, at one and the same knitting machine. In such cases, the monitoring and detection of the individual yarn amounts until now is impossible with reasonable control equipment and apparatus efforts. Basically, however, consecutive, sequential or final information of the yarn amounts of such specially equipped knitting machines would be important for the knitting mill owner and the specialised personnel in order to judge and optimise the efficiency of the production, to realise fluctuations of production parameters during the production early on, to save time and labour effort for the pre-setting, changes of the setting and adjustment, and to achieve an optimisation of the quality and continuous high quality with fewer defective goods.
According to a method known from DE 82 24 194 U the yarn amount is measured per revolution of the knitting machine. For this purpose a scanner is co-acting with a band commonly driving all feeding devices provided at the knitting machine. The method can only be used for positive feeding devices at the knitting machine, which positive feeding devices commonly are driven by a band. All feeding devices operate with equal feeding rates and with identical yarn conveying principles.
According to a method as known from EP 0 489 307 A, the entrance speed of each yarn into a knitting system is constantly maintained equal or proportional to an entrance speed which is predetermined by a self-learning cycle on the basis of a masterpiece. Control of the entrance speeds is carried out during the production run of the knitting machine. Furthermore, during the production run a driven actuator, e.g. a roller, pulls the yarn from a storage bobbin such that the yarn is fed during the production run with a constant yarn quantity. The actuator determines the entrance speed of the yarn. The self-learning cycle is carried out prior to the start of the production run of the knitting machine without using the actuators in order to find out respective decisive yarn quantities. The actuators correspond to positive feeding devices. The actuators are identical among each other and operate with equal yarn conveying principles. A sensing roller is provided as a sensor at each yarn between the actuator and the yarn guide into the knitting system of the knitting machine. The sensing roller measures the yarn quantity and informs a console unit or a microprocessor also provided for the drive control of the respective actuator. The roller sensing the yarn quantity is an undesirable additional mechanical load for the yarn and emits imprecise measuring results due to unavoidable slip.
Further prior art is contained in EP 0 752 631 A, EP 0 959 742 A, EP 0 600 268 A, DE 82 24 194 U, EP 0 420 836 A, EP 0 385 988 A, EP 0 489 307 A.
The setting procedure of a knitting machine prior to production or after a change of the settings is particularly time consuming and requires special knowledge, particularly when the knitting machine is equipped with non-positive feeding devices which may even originate from different producers, and even differentiate from each other in terms of the respective yarn conveying principles, because each feeding device including its peripheral, yarn influencing accessory assemblies has to be associated with the respective knitting system and has to be adjusted to an individual and optimum operation. In this case simply achievable information on the individual yarn amounts was of invaluable advantage since a yarn amount deviating from a target indicates for such a feeding device not only a fault condition or a trend, but even allows a direct conclusion to the kind of a fault which then could be corrected rapidly and at that point. Furthermore, in view of this aspect there is considerable demand for a method for an efficient monitoring adjustment of the production for knitting machines having non-positive feeding devices, and for a device allowing for a simpler pre-setting, changing of settings and the adjustment of a knitting machine or even of a knitting machine series.
It is an object of the invention to provide a method of the kind as disclosed above as well a device for carrying out the method which allow a simple and comfortable monitoring/adjustment of the production despite the fact of the existence of non-positive yarn feeding principles of feeding devices of different types which even operate according to different conveying principles.
By carrying out the method such that each individual yarn amount is continuously measured with the help of detected actual rotational signals of the feeding device, a sufficiently precise yarn amount information is achieved from the actual rotational signals under consideration of the storage body circumferential length and without the need to use separate sensors for these tasks. Actual rotational signals are used in any event which result from the operation of the feeding device. Even though several non-positive feeding devices are used at the knitting machine which feed yarn of different qualities and/or elasticity according to at least two different yarn conveying principles, and which even may originate from different producers, the actual rotational signals can be detected easily. According to the method, the individual yarn amounts are detected precisely and deliver information for the monitoring/adjustment of the production. One reason for different feeding device types is that the feeding devices have to cope with different yarn tensions and/or yarn speeds, with one type having better capabilities than another type. Within the frame of the method the individual yarn amounts are not measured primarily to gain the total yarn amount but to indicate with the help of the yarn amounts certain fault conditions in order to allow one to survey and optimise the production in a simple way. As a secondary product, the total yarn amounts can also then be detected with little additional effort. The method is expedient for circular knitting machines, however, it also can be implemented for flat knitting machines. The method concentrates on the recognition that especially in the case of non-positive feeding devices the actual fed yarn amounts allow one to draw conclusions as to a proper operation in the knitting system, at the feeding device and in the yarn path and in view of trends towards a fault condition or even conclusions of certain fault conditions.
From the continuous or final comparison of the individual yarn amounts with corresponding and predetermined target yarn amounts, e.g. of a masterpiece, and within at least one range of tolerance, the operation of each feeding device and at the associated knitting system can be monitored precisely. Critical production conditions and even the reasons therefor can be determined, and measures can be initiated even during the production or after the production in order to correct fault conditions. The method may be upgraded in that a fault condition detected with the help of the comparison of the yarn amounts, which fault condition in most cases is associated with a certain kind of a fault, is corrected automatically, e.g. within a closed adjustment regulation loop using the result of the comparison as the regulation guiding value. Such adjustments can be carried out at the knitting system or at the feeding device or at the peripheral accessory assemblies of the feeding device, because mainly those operation elements mentioned as a selection have an influence on the yarn amount, such that a fault condition occurring at one of these operation elements can be shown ideally with the help of a tolerance variation of the yarn amount in comparison to the yarn amount of the masterpiece. In this case it is important to adapt the width of the range of tolerance used for the comparison even to parameters of the yarn quality and/or the yarn path.
By means of the computerised monitoring/adjustment device, a user friendly tool is offered to the specialised personnel at the knitting machine (circular knitting machine or flat knitting machine) which is important in view of efficient production and short pre-setting procedures, and which may be used to comfortably adjust the pattern of the associations of the feeding devices out of the stock directly at the user surface. So to speak, each feeding device is fictively taken from the stock in view of the yarn quality/elasticity and the position relative to a knitting system and then is operatively associated already in the user surface to the respective knitting system intended for processing this yarn. This allows one to considerably simplify the pre-setting or a change of the setting of the knitting machine, to save time, and to reduce the labour effort. With the assumption that e.g. the circular knitting machine is equipped with a sufficiently huge stock of non-positive feeding devices among which there are at least two operating according to different yarn conveying principles, the device creates a link between the feeding devices and the circular knitting machines as needed for an efficient production, and such that troublesome setting operations at the feeding devices and/or in the machine control are reduced to a minimum. It is obvious that association patterns specific for a respective knitted article may be stored and used or retrieved again upon demand or that an association pattern created for knitted goods in the user surface can be transferred to each further knitting machine producing the same knitted article. For example, a keyboard or the like and/or the display designed as a touch screen may be used as the input/indication-section of the unit.
Expediently, the yarn amounts are measured by detected actual rotational signals, e.g. calculated, and are compared with corresponding target yarn amounts. Since among different yarn feeding device types each comparison is carried out only in view of yarn amounts of one feeding device type, it is possible that the yarn amounts of differing feeding devices are measured in different ways such that a measured value of a yarn amount of one type of a feeding device first does not correspond to the same measured value of the yarn amount of another type. First when the total yarn amount or a yarn amount specific for the knitted goods is to be determined, a conversion or conversion calculation is made into equal length units or weight units. According to the method it is possible to carry out each comparison with the masterpiece with the help of the detected actual rotational signals, e.g. with the help of the type of the signal and/or the number of signals and/or the frequency of the signals in order to detect an individual fault condition or a fault trend, before real yarn amounts or yarn weights are determined.
The method primarily is adapted to the production of knitted goods in circular knitting machines having different feeding device types which operate simultaneously or subsequently and with non-positive yarn feeding principles according to at least two different yarn conveying principles. For example, less elastic yarn is fed by a feeding device including a rotatable storage body, while more elastic yarn is fed by a feeding device including a stationary storage body and a winding element which rotates. Such differing types are selectively used depending on the expected yarn tension and/or the yarn speed. Such equipment of a circular knitting machine is expedient e.g. for so-called body stockings or jacquard knitted goods. However, this equipment may also be of advantage for other high quality knitted goods in which differing yarn qualities and/or different elastic yarns are knitted. The same prerequisites could even be used for flat knitting machines.
In case of a feeding device having a rotating storage body, one actual rotation signal may be scanned per revolution of the storage body. This signal then represents a yarn amount corresponding with the circumferential length of the storage body. In order to achieve a higher resolution it also is possible to scan a predetermined number of actual rotational signals per revolution of the storage body, each of which represents the same part of the circumference of the storage body. In order to simplify the control, the scanning e.g. is carried out by scanning the rotation of the drive motor.
In case of a feeding device having a stationary storage body, expediently, a plurality of actual rotational signals are scanned which represent equal parts of one yarn winding. Since in the case of a very elastic yarn the windings resting on the stationary storage body may be stretched out, the measurement is more precise if the withdrawn yarn itself is allowed to generate the actual rotational signal.
In view of the method it is expedient to adjust the width of the range of tolerance used for the individual comparison in case of a more elastic yarn, e.g. larger than in the case of a less elastic yarn, since in case of a more elastic yarn parameters occurring along the yarn path gain bigger influence.
According to the method an individual yarn amount comparison cannot only be carried out within a single range of tolerance, but subsequently or parallel even within several ranges of tolerance having increasing widths. In this way and by using a narrow range of tolerances, first a trend can be displayed from the comparison with the development of the yarn amount in the masterpiece in order to derive an alarm signal upon demand, which alarm signals call the specialised personnel to particularly monitor the yarn path, the feeding device or the knitting system, respectively. The next and broader range of tolerance can then be used to derive an adjustment measure in case that the range of tolerance is exceeded. Then the specialised personnel manually carries out adjustments along the yarn path, at the feeding device or at the knitting system, respectively, or such adjustments are even initiated automatically. The largest range of tolerance, finally, may be used to switch off the knitting machine, because an out of tolerance condition then indicates a fault condition which can no longer be corrected.
Especially in the case of a more elastic yarn, conditions in the yarn path may be monitored continuously, e.g. with the help of the tension of the yarn, and may be used e.g. for the adaptation of the width of the range of tolerance used for the comparison and/or to process the scanned actual rotational signals. In case of feeding devices having a rotating storage body, the yarn tension could be measured at the withdrawal side, which yarn tension is important for controlling the drive motor, and then could be used for tuning the actual rotational signals in view of very precise measurements of the yarn amount.
On a further user surface of the display of the production monitoring/adjusting device, the operations of the feeding devices associated with the respective knitting systems may be displayed during the production of a knitted article by the individual yarn amounts in comparison with yarn amounts of the masterpiece, preferably within ranges of tolerance depending e.g. on the yarn quality and/or the respective yarn conveying principle. This expediently may be realised with the help of pictogram strips or bars representing the yarn amounts. The strips or bars are associated with addressed or identified feeding devices and the associated knitting system. An out of tolerance condition optically may be highlighted and e.g. highlighted by a light signal or in acoustic fashion.
Existing knitting machines of such types may be simply retrofitted with the monitoring/adjustment device for the production. In such a case, expediently, the device is positioned within a housing beside the knitting machine or in a cut-out of the foot part of the knitting machine.
Alternatively, the monitoring/adjustment device may be integrated with the display and the inputting/indicating section into the main control system of the knitting machine. This is of advantage in order to allow one to use the same actuation elements for the monitoring/adjustment and even the display of the machine control as otherwise used for the machine control.
Knitting machine feeding devices having rotatable storage bodies are used for less elastic yarns, while feeding devices having stationary feeding bodies, a rotatable winding element, and a counting sensor assembly for yarn windings at the withdrawal side are used for more elastic yarns. In order to allow one to produce different knitted goods, it is recommended that a stock of feeding devices be provided at the knitting machine which is larger than the number of feeding devices operating in production.
The device, expediently, allows one to configure a user surface in which for one or more produced knitted goods, the total yarn amount/the single yarn amount or total yarn weight/single yarn weight can be shown in length units and/or weight units.
Since there is a plurality of data which has to be transmitted rapidly for monitoring/adjusting the production, since many connection locations are needed for fetching data and processing data, and since the cabling should be as simple as possible and should assure high safety of the operation, it is expedient to interlink the knitting machine and its control, the production monitoring/adjustment device, and the feeding devices including the peripheral accessory assemblies in a data bus system, preferably in a rapid CAN-bus system. The feeding devices may be connected in fixed or selective fashion to the bus via interface adapters. Those adapters, at least for some of the used feeding devices, are designed such that the derived needed actual rotational signals for the measurement of the yarn amount are taken by them directly at the feeding device or as pulses which are available in any event from the operation of the feeding device.